By chance?

[Rahn127]

Usually "chance" means an unknown probability.

There is a 50% chance of rain.
There is a chance that the woman I'm about to talk to will say yes when I ask her out for a date.
There is a chance that abiogenesis will be figured out in the next 50 years.

So when you say that something is by chance you are saying that the actual outcome or end result by which it happens is unknown at this time.

I would say that there are some processes that we don't know, but there are quite a few that we can demonstrate to be true to the best of our knowledge.

Being able to demonstrate truth means we can reproduce the results or we can reasonably show how we came to our conclusions by showing the evidence of our findings.

Evolution isn't by chance because we know the mechanisms by which life changes over time.

The universe, as much as we can tell, operates under the forces of physics. Physics isn't by chance either. We have slowly, over time, increased our knowledge about how bodies in motion react to each other through gravitational forces.

We observe nature and discover what appears to be physical laws of motion. In every discipline of science we observe the world around us and make our conclusions about those observations, supplying evidence to support our conclusions.

We welcome anyone to prove our conclusions wrong.
Our entire system of peer review hinges on it.

Show your work. Provide your evidence and let others attempt to rip it to pieces. Walk the gauntlet and join every other scientist in the world.

Chance rarely has anything to do with it.